I see this same question asked about 2-3 times each week and I would like to share what I think THE Method all DOs out there should use to make this decision.
I would say this fits 99%+ of DO's.
ALL DO's SHOULD take the USMLE UNLESS you fall into 1 of 3 three categories
1. You KNOW 100% that you want to do a primary care specialty.
or
2. You KNOW 100% that you want to do an Osteopathic residency (no matter what specialty you want to do)
or
3. You are in danger of failing/doing poor on USMLE(read below)
Most people dont know how they will do on USMLE before taking it, so if you fall under #3 then do the following:
1. Plan on taking both test and sign up for BOTH of them
2. About 1 month before the USMLE take either the NBME 2 or 3 practice test on the NBME website($45 each).
3. Decide if you think it is worth it to take the USMLE from your NBME score- I would probably make your cut off at 1 month be about 185-200 to be safe with a worth while score. If you make below that, its your call. Some people can bring their score up 30+points in a month, but some can only bring it up a little. Bottom line is with a USMLE score below a 200 you probably wasted your time/money. Personally I would only consider it really worth it if you score 215+.
If you dont make the cut off at 1 month, then call and cancel. I think you only loose about $50 by canceling within a certain amount of time.
So worst case scenario- you sign up for both, then do terrible on the NBME practice test, so you cancel and loose about $50 for canceling and $45 for the NBME test.
Best case scenario- YOU TOTALLY SURPRISE YOURSELF WITH HOW WELL YOU DID ON THE USMLE AND LAND AN AWESOME RESIDENCY.